<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>圆环转动动画</title>
    <link rel="stylesheet" href="../common.css">
    <style>
        :root{
            --color: orange;
            --lineColor: rgba(102,163,224,0.2);
        }
        section{
            position: relative;
            width: 200px;
            height: 200px;
        }
        section::before{
            content: "";
            position: absolute;
            /* 居中 */
            height: 10px;
            width: 10px;
            border-radius: 100%;
            border-top: 1px solid orange;
            top: 50%;
            left: 50%;
            margin-top: -5px;
            margin-left: -5px;
            animation: turn 1s infinite linear;
            filter: drop-shadow(0 0 2px var(--color))
            drop-shadow(0 0 5px var(--color)) drop-shadow(0 0 10px var(--color))
            drop-shadow(0 0 20px var(--color));
        }
        .box,
        .box::after,
        .box::before{
            border: 2px solid var(--lineColor);
            border-left: 2px solid var(--color);
            border-right: 2px solid var(--color);
            border-radius: 50%;
        }
        .box::after,
        .box::before{
            position: absolute;
            content: "";
            left: 50%;
            top: 50%;
        }
        .box{
            width: 200px;
            height: 200px;
            position: relative;
            animation: turn 1s linear infinite;
            transform-origin: 50% 50%;
        }
        .box::before{
            width: 180px;
            height: 180px;
            margin-top: -90px;
            margin-left: -90px;
            animation: turn2 1.25s linear infinite;
        }
        .box::after{
            width: 160px;
            height: 160px;
            margin-top: -80px;
            margin-left: -80px;
            animation: turn 1.5s linear infinite;
        }
        .box-circle{
            border: 2px solid var(--color);
            opacity: 0.9;
            border-radius: 50%;
            position: absolute;
            left: 50%;
            top: 50%;
            transform-origin: 50% 50%;
            transform: translate(-50%,-50%);
            width: 100px;
            height: 100px;
            animation: rotate 3s linear infinite;
            animation-delay: var(--d);
        }
        @keyframes turn {
            100%{
                transform: rotateZ(-1turn);
            }
        }
        @keyframes turn2 {
            100%{
                transform: rotateZ(1turn);
            }
        }
        @keyframes rotate {
            100%{
                border: none;
                border-top: 2px solid var(--color);
                border-bottom: 2px solid var(--color);
                transform: translate(-50%,-50%) rotate3d(0.5,0.5,0.5,-720deg);
            }
        }
    </style>
</head>
<body>
    <section>
        <div class="box"></div>
        <div class="box-circle" style="--d: 0.2s"></div>
        <div class="box-circle" style="--d: 1.2s"></div>
        <div class="box-circle" style="--d: 2.2s"></div>
    </section>
</body>
</html>